3

I'm reading a code that uses Arduino as a webclient and when he tries to catch the info from the site, he uses a callback with the following parameters:

static void response_callback (byte status, word off, word len)

Can anyone explain me how does each one of this parameters work exactly?

PS.: The example I got it from:

#include <EtherCard.h>

#define HTTP_HEADER_OFFSET 0
static byte mymac[] = {0x12,0x34,0x56,0x78,0x90,0xAB};
char website[] PROGMEM = "www.yourwebsite.com";

byte Ethernet::buffer[700];
static uint32_t timer = 0;

static void response_callback (byte status, word off, word len) {
  Serial.print((const char*) Ethernet::buffer + off + HTTP_HEADER_OFFSET);
} 

void setup () {
  Serial.begin(57600);

  if (!ether.begin(sizeof Ethernet::buffer, mymac, 10))
  {
    Serial.println("Failed to access Ethernet controller");
    while(1);
  }
  else
    Serial.println("Ethernet controller initialized");
  Serial.println();

  if (!ether.dhcpSetup())
  {
    Serial.println("Failed to get configuration from DHCP");
    while(1);
  }
  else
    Serial.println("DHCP configuration done");

  if (!ether.dnsLookup(website))
  {
    Serial.println("DNS failed");
    while(1);
  }
  else 
    Serial.println("DNS resolution done"); 

  ether.printIp("SRV IP:\t", ether.hisip);
  Serial.println();
}

void loop() {
  ether.packetLoop(ether.packetReceive());

  if (millis() > timer) {
    timer = millis() + 5000;
    ether.browseUrl("/", "yourpage.php", website, response_callback);
  }
}
Edgar Bonet
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Vinícius Affonso
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1 Answers1

1

Apparently, the callback is executed on every packet which arrives by the browseUrl call.

"off" and "len" are pointers to the Ethernet buffer holding the data. "Off" are the initial value (offset) and "len" (length) is the amount of data received.

"byte status", I am not sure what it means, but it's very likely will be some kind of error code. It's not being used in any sample I am seeing, so I am really wondering what it means...

Check this link for a fully working sample

Callback here are called browseUrlCallback1 and browseUrlCallback2.

Can't figure out a link with the detailed documentation. If someone has it, please post it.

fabrosell
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